关键词: 天然气渗漏 , CH₄ 水合物 , CO₂ , N₂ , 置换 , 机理

Abstract: In order to simulate the effect of leakage of natural gases with high contents of CO₂ and N₂ on the methane hydrates reservoir overlying, the replacement experiments of CH₄ hydrates by using two groups of gas mixtures were observed with a selfdesigned device at 277.15 K, initial pressure 6.37 MPa and at 275.15 K, initial pressure 4.30 MPa respectively. The quartz sand and 3.5% NaCl aqueous solution were mixed to simulate seafloor and two groups of gas mixtures, one has high contents of N₂ and another has high contents of CO₂, were chosen from northern South China Sea. Experimental data show that the variation of CO₂ is the most and the variation of N₂ is much less. It indicate that CO₂ plays a leading role. The replacement efficiency of two groups of gas mixtures at different experimental conditions are 8.64% and 20.71% at 140 h of experiment. Based on the experimental results, a simple replacement mechanism of CH₄ hydrate dissociated with CO₂ in porous medium system was proposed.

Key words: Leakage of natural gas,    ,  CH₄ hydrate,    ,  CO₂,    ,  N₂,   ,  Replacement,    , Mechanism